Over 80% of married women who own diamond jewelry were given their diamond(s) as a gift, usually by a man. For single women, 60% of their diamonds were given to them by men.

Diamond engagement rings were beloved by the Victorians but by the late 1930s, the demand was falling in the United States, which then, as now, was the world's largest market for diamond jewelry.

Sir Ernest Oppenheimer, head of South Africa's biggest diamond company De Beers, hired a New York advertising agency to create a demand for diamond engagement rings. The campaign was based on the concept of a diamond being for eternity and in 1948, a copywriter came up with the line, "A diamond is forever."

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Within three years of the launch of that slogan, which has been described as one of the greatest advertising slogan of the 20th century, 80% of American marriages were marked with a diamond engagement ring.

From the 1940s, De Beers promoted diamonds and diamond jewelry by organizing design contests. Winners included Julius Cohen, who worked for the famous New York firm ofHarry Winston before setting up his own company.

In 1999, De Beers' millennium campaign began, with advertising directed atmen. "Show her you'll love her for the next thousand years" was a slogan that tapped into two important facts: ­ men buy diamonds and they buy them for women.

Other admen in the U.S. came up with "Which millennium are you waiting for?", "Everythousand years or so it's nice to get her something really special forChristmas" and "Isn't she worth two months' salary?" The time period in the ads was tweaked internationally to reflect what men in different parts of the world would pay for diamond jewelry for their women, so in Japan it was three months, in Europe one.

De Beers spends $US200 million a year advertising diamonds and it pays off:its millennium campaign increased its sales of rough (uncut diamonds) in thefirst half of 2000 by 44% from $2.4 billion to $3.5 billion.

One of the most influential forms of advertising is the wearing of diamond jewelry by the rich and famous. In many cases it need not even be their own.

Hosting the 1998 Academy Awards, Whoopi Goldberg wore $US41 million worthof diamond jewelry lent by Harry Winston. They included a 107.18 carat ring worth $US15 million. At the same Oscars, Geena Davis wore a Winston diamond ring worth $2.6 million and Gwyneth Paltrow wore a $US160,000 Winston necklace, later bought for her by her father. Winston's sold 25 copies at US$175,000.

And in case anyone forgot which state former US President Bill Clinton camefrom, his wife, Hillary Rodham Clinton, wore a reminder at the 1992 and 1996presidential inaugurations.

It was a ring designed by Henry Dunay. Based on the topography of Arkansas,it was set with a 4.23 carat uncut canary diamond found in a state park in Arkansas.

Diamond jewelry is for keeps, so whether its bought as an investment or simply for adornment, its value will continue to grow for eternity.